1. Field of the Invention
The invention concerns a relay and more particularly a safety relay with an electrically insulating carrier part and an electromagnetic drive arranged on the carrier part, at least one control contact and at least three load contacts, both the load and control contacts being forcibly guided. In such a relay, the contacts are individually comprised of two essentially parallel, flat contact springs, each spring comprising a contact head, a spring foot at a distance to the contact head and at least one fastener part connected to the spring foot, for example one or two pins. The spring feet of the contact springs are rigidly fixed on the carrier part. The invention also concerns a three-phase supply network capable of being switched by such a safety relay and the circuitry associated with such a safety relay.
2. Brief Description of Art
As used herein, the term xe2x80x9cforcibly guidedxe2x80x9d refers to the property of being linked by a common movable comb. Therefore, a forcibly guided relay is one in which the contacts are mechanically linked by a common movable comb, connected with the drive and in which at least one working contact and one resting contact are provided. In such a relay, one of the contact springs of each contact is next to a fixed stop in the vicinity of the head, and the other contact spring is engaged in such a way in the comb that it is mechanically linked to the movements of the comb. In this way, it is assured that if a contact is welded, either this contact is broken, or the comb cannot be moved and thus the other contacts must remain in the position produced by the welded contact.
The term xe2x80x9csafety relayxe2x80x9d means a relay in accordance with standard EN (European Standard) 50205. In a safety relay according to standard EN 50205, the air paths and leakage paths between the control contact and the load contact correspond to the requirements of standard IEC 61810-5 and IEC 664-1. The contents of these standards incorporated in their entirety herein by reference.
For switching electric devices consuming electrical current wherein a high safety standard must be met, two safety relays and two downstream-connected contactors are used. Examples of such current consumers include three-phase current motors. Such circuitry is appropriate for devices having loads, for example, of more than 6 kW. However, devices with loads of approximately 1 to 4 kW are also connected in the described manner and the contactor used therein would be suitable for significantly greater loads. Three-phased motors with a load current, for example, of 5.6 A (constant current) and a switching-on peak-current of approximately 40 A cannot be switched with known safety relays without the provision of an overdimensioned contactor. This requires a nonnegligible expenditure for wiring. In such wiring, each relay and contactor is a relatively expensive part in the production of the circuitry and represents separate possible sources of error.
It is the object of the present invention to increase the safety of switching current, such current switching relative to three-phase mains current, while reducing the structural volume of the required parts. For this purpose, in particular, the number of parts for switching and the possible sources of error in the circuit of current consumers, especially of short-circuit-resistant, three-phase electric motors of 1 to 4 kW power, will be reduced. In addition, a forcibly guided relay will be created, which is designed for voltages of more than 110V or 250V, particularly the 200 or 400V relative voltage between phases that occurs in three-phase mains current, that fulfills the requirements of a safety relay with forcibly guided contacts.
A reduction in the number of parts and a reduction in the number of error sources will be resolved according to the invention by using a forcibly guided safety relay for switching the three phase circuit of a three-phased mains voltage connected to the three load contacts. Appropriately, two relays connected in series are used for the synchronous switching of the three phases in the two relays. By the use of the relay for the direct switching of the consumer current, two contactors connected downstream to the relay and the corresponding wiring of the contactors can be dispensed with. The reduction in the number of parts is accompanied by a reduction in possible sources of error. The double design of the relay serves for safety. It is immaterial whether the two relays are connected in series or if one double relay is utilized.
In a circuit for a three-phase main-current consumer, particularly a short-circuit-resistant electric motor with a forcibly guided safety relay, the three phases of the mains current are connected to the load contacts of the safety relay according to the invention. Here also, for purposes of safety, two safety relays connected in series as two separate relays or together in the form of a double relay are appropriately provided.
Accordingly, one aspect of the invention is drawn to a safety relay comprising an electrically insulating carrier part, an electromagnetic drive arranged on the carrier part, at least one control contact arranged on the carrier part, at least three load contacts arranged on the carrier part. Each of the load and control contacts is forcibly guided by a common comb connected with the electromagnetic drive and has two contact springs, each of the contact springs comprising, a contact head, a spring foot at a distance from the contact head, and at least one fastener part connected with the spring foot. The contact springs are supported solidly with the spring foot in the carrier part. At least one of the contacts forms a working contact and another one a resting contact. A rigid stop is arranged on the carrier part next to which is located the contact head the rigid stop being in the vicinity of one of the contact springs, the other one of the contact springs of the contact engaging the comb in such a way that the movement of the contact spring is mechanically linked with the movements of the comb. At least one insulating dividing wall for separating the contact springs of the load contacts is reaching from the spring foot at least to the vicinity of the contact head and extending from one side to the other of the safety relay. The dividing wall has an offset on the sides bent in opposite directions. A continuous separating wall embracing the adjacent contact springs of the load contacts is formed by the bent offsets connecting the dividing wall with one of the adjacent dividing walls such that the dividing walls and the offsets form a continuous separating wall.
A second aspect of the invention is drawn to a three-phase supply network that comprises at least one safety relay to switch the three phases of the supply network. The relay comprising an electrically insulating carrier part, an electromagnetic drive arranged on the carrier part, at least one control contact arranged on the carrier part, at least three load contacts arranged on the carrier part. Each of said three load contacts is connected to one of said three phases and each of the load and control contacts is forcibly guided by a common comb connected with the electromagnetic drive. Each load and control contact has two contact springs, each of the contacts springs comprising, a contact head, a spring foot at a distance from the contact head, and at least one fastener part connected with the spring foot. The contact springs are supported solidly with the spring foot in the carrier part. At least one of the contacts forms a working contact and another one a resting contact. A rigid stop is arranged on the carrier part next to which is located the contact head. The rigid stop being in the vicinity of one of the contact springs, the other one of the contact springs of the contact engaging the comb in such a way that the movement of the contact spring is mechanically linked with the movements of the comb.
A third aspect of the invention is drawn to an electrical circuit for switching a three-phase main-current consumer the three phases of the current supply network being connected to three load contacts of a safety relay comprising an electrically insulating carrier part, an electromagnetic drive arranged on the carrier part, at least one control contact arranged on the carrier part, and at least three load contacts arranged on the carrier part. Each of the load and control contacts is forcibly guided by a common comb connected with the electromagnetic drive and has two contact springs. Each of the contact springs comprises a contact head, a spring foot at a distance from the contact head and at least one fastener part connected with the spring foot. The contact springs are supported solidly with the spring foot in the carrier part. At least one of the contacts forms a working contact and another one a resting contact. A rigid stop is arranged on the carrier part next to which is located the contact head. The rigid stop being in the vicinity of one of the contact springs, the other one of the contact springs of the contact engaging the comb in such a way that the movement of the contact spring is mechanically linked with the movements of the comb.
A forth aspect of the invention is drawn to a process for switching the three phases of a three-phase supply network, the three phases being switched by a safety relay comprising an electrically insulating carrier part, an electromagnetic drive arranged on the carrier part, at least one control contact arranged on the carrier part, and at least three load contacts arranged on the carrier part. Each of the load contacts is connected to one of the three phases. Each of the load and control contacts is forcibly guided by a common comb connected with the electromagnetic drive and has two contact springs, each of the contacts springs comprising, a contact head, a spring foot at a distance from the contact head and at least one fastener part connected with the spring foot. The contact springs are supported solidly with the spring foot in the carrier part. At least one of the contacts forms a working contact and another one a resting contact. A rigid stop is arranged on the carrier part next to which is located the contact head. The rigid stop being in the vicinity of one of the contact springs, the other one of the contact springs of the contact engaging the comb in such a way that the movement of the contact spring is mechanically linked with the movements of the comb.
Preferably, in a relay of the present invention, the individual contact springs of the load contacts are separated from one another by an insulating dividing wall reaching from the spring foot to at least the vicinity of the contacthead and extending from one side of the relay to the other. The dividing wall is bent in opposite directions on the sides and each bent part is connected with another of two adjacent dividing walls. In this way, the dividing walls and the bent parts together form a continuous separating wall meandering about the contact springs of the load contacts. With this constructive measure, the prerequisites for a constricted space with respect to leakage paths between the load contacts can be fulfilled, since the leakage paths between the spring feet of the contact springs of adjacent contacts extend around a bent part. The meandering is achieved by two cast shapes with opposite gearing. These shapes can be separated and again combined by a translation crosswise to the direction of movement of the comb.
Preferably, the contact springs of the control contacts have a smaller cross section than those of the load contacts. This results in a savings of material and space for the control contacts. In other words, the cross-sections of the springs of the load contacts are larger than those of the control contacts. This configuration allows for higher current flow with less resultant heating of the springs of the load contacts. In addition, the spring force of the springs of the load contacts is greater and thus the force for loosening the contact is increased and thus greater weldings of the contact heads can be loosened, than in the case of smaller spring cross sections.
The contact springs of the load contacts are appropriately arranged one behind the other in a linear row in the direction of motion of the comb and take up the same width as two control contacts next to one another. Such an arrangement permits simple control of the contact springs with a common comb.
Advantageously, the stop for the contact springs, which are not engaged with the comb, is formed by a lip at the dividing wall between the contact springs of a contact. Owing to the bent parts, the dividing wall is very stiff and is able to withstand forces even in a heated state, to reliably retain the contact spring. The stop can be formed on one or the other of the two geared cast forms according to an example of embodiment. In this way, various combinations of resting and working contacts can be achieved by slight changes in the cast shape.
Preferably the planar dividing wall between the contact springs of different contacts reaches up between the contact heads. Thus, a chamber system is formed for each individual contact spring by the dividing walls which assures a secure separation of the contacts from one another even in the case of increased contamination by any burnt-off material of the contact heads. The planar dividing wall between two adjacent contacts extends beyond the contact heads in order to lengthen the air path between these contacts.
In a preferred embodiment of the invention, cross-pieces are formed on the comb between the contact head at the contact spring engaging in the comb and the dividing wall between two contacts. The cross-pieces are aligned parallel to the dividing wall. They also lengthen the air path between adjacent contact springs of different contacts. Due to the crosspieces, a minimum structural height of the relay and, at the same time, the desired path elongation of the air path between the ends of adjacent contact springs of different contacts on the head side are achieved.
The planar dividing walls between the contact springs of the same contact and the bent parts are preferably of equal height. Bent parts of lower height would adversely affect the stiffness of the dividing wall, while greater heights would impede the view onto the contact heads.
Advantageously, in the case of the contact springs of the load contacts, the spring foot is displaced laterally with respect to the contact head such that the fastener parts of the two contact springs of one load contact are arranged at opposite edges of the carrier part, but the heads are arranged in between at a central line. The fastener parts of adjacent contact springs thus are arranged at the opposite edges of the relay. The fastener parts on the same end of the relay are arranged at double the spring distance. By this construction, even though the relay is built very compactly, the required and prescribed safety distances between the fastener parts are met. Preferably, the spring feet are arranged near the open side of the chamber system so that slots for receiving the contact springs provided in the carrier part cut to as small a depth as possible. The load contacts advantageously each have two fastener parts, in order to have double the connection surface with a connection part, e.g., a printed-circuit board or a relay plug, as compared to springs with only one fastener part.
Advantageously, the control contacts are arranged next to one another with reference to the direction of motion of the comb and are separated by a planar partition wall extending in the direction of motion of the comb. With this space-saving configuration a chamber system is achieved that ascertains a sufficient separation of the contacts. In an even smaller construction, but still providing for a sufficient separation of the contacts, the comb is provided with an elongated opening, the partition wall extending through this opening with its comb-side edge. Having the partition wall forked on its comb-side edge allows for an even more compact construction. The forking forms a channel which extends lengthwise to the direction of motion of the comb. A covering is provided having a rib which extends into the channel and between the forking. With this construction, a labyrinthine elongation of the air path between two control contacts is achieved, which in turn permits a minimal structural height of the relay. Even when the contact springs of the load contacts are also bent relative to their fastener part-contact head axis, so that the contact head is arranged at a central line and the two fastener parts on one or the other edge of the carrier part, the contacts springs of the load contacts are still essentially planar and of the same configuration. The contact springs differ only by the length of an end portion on the head side projecting over the contact head such that the active contact springs engage with their long end portions into the comb, but the passive contact springs with their short end portions do not.